TMP421AIDCNR from Texas Instruments, in a SOT-23-8. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	DXP	input	Positive connection to the external remote temperature-sensing diode/transistor. Sources bias current (up to 120 µA) into the remote junction for temperature measurement.
2	DXN	input	Negative connection to the external remote temperature-sensing diode/transistor. Return path for the remote-sensor bias current.
3	A1	input	Address-select pin. Tie to GND, V+, SDA, or SCL to set the SMBus slave address (7-bit address prefix 100 11xx per Package Information table).
4	A0	input	Address-select pin. Tie to GND, V+, SDA, or SCL to set the SMBus slave address (7-bit address prefix 100 11xx per Package Information table).
5	GND	power_in	Ground reference for the device (0 V).
6	SDA	bidirectional	SMBus/I²C serial data line, open-drain. Requires an external pull-up resistor to V+. Supports clock frequencies up to 3.4 MHz.
7	SCL	input	SMBus/I²C serial clock line, open-drain. Requires an external pull-up resistor to V+.
8	V+	power_in	Positive supply voltage input, 2.7 V to 5.5 V for TMP421 (2.55 V to 5.5 V for TMP421C). Decouple locally to GND.

Key specifications

Parameter	Value
Manufacturer	Texas Instruments
Package	SOT-23-8
Category	Sensor
Pins	8

Ordering variants

Same part, different packaging or reel option.

TMP421AIDCNR
TMP421AIDCNT
TMP421AIDCNRCYZDR
TMP421AIDCNRCYZDT

CAD (KiCad official)

Symbol: TMP421AIDCNR
Footprint: Package_TO_SOT_SMD:SOT-23-8
3D model: SOT-23-8 (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Texas Instruments datasheet (35 pp, sha256 9767344d67270d4c, retrieved 2026-08-17, tier: manufacturer)
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF